feat(desktop): 工业化升级 A —— 设计系统地基（primitives + lucide + 语义令牌）

把"手搓内联 class + Unicode 字符图标"换成统一组件与真实图标，为后续工业化打底。

- 依赖：装 lucide-react（描线图标，按需 tree-shake）
- 令牌：tailwind.config 加语义色 brand/accent/success/warn/danger + 圆角档位；
  强调色字面量(violet/cyan/emerald…)收敛到令牌，便于整体换肤
- primitives（src/ui，零重依赖自建）：Button/Input/Textarea/Select/Field/Card/Panel/
  Badge/Dot/Tabs/Skeleton/EmptyState/Dialog/Toast(+useToast)/cn，桶文件统一引入
- 迁移：TopBar/LeftNav/BottomDrawer + Home/Report/Runs/Kb/Placeholder/ExecTrace/
  MemoryPanel/StudioView 全部换 primitives + lucide 图标；导航/能力卡/按钮告别
  ▤◆▣▦ 等 Unicode 字符；错误改用全局 Toast；空状态用 EmptyState
- App 包 ToastProvider

验证：tsc + vite build 通过；浏览器(Preview)走查工作台/报告页——真实图标、统一卡片/
按钮/输入；跑报告端到端正常（执行轨迹 lucide 状态图标点亮、章节耗时/字数/检索片段、
完成弹 Toast + 下载 Word）。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

sundynix-desktop/frontend/src/ui/Input.tsx

@@ -0,0 +1,32 @@
+import type { InputHTMLAttributes, TextareaHTMLAttributes, SelectHTMLAttributes, ReactNode } from "react";
+import { cn } from "./cn";
+
+const fieldBase =
+  "w-full rounded-md border border-line bg-ink-950 text-sm text-slate-200 placeholder:text-slate-600 transition focus:border-brand focus:outline-none focus:ring-1 focus:ring-brand/40 disabled:opacity-50";
+
+export function Input({ className, ...rest }: InputHTMLAttributes<HTMLInputElement>) {
+  return <input className={cn(fieldBase, "h-9 px-3", className)} {...rest} />;
+}
+
+export function Textarea({ className, ...rest }: TextareaHTMLAttributes<HTMLTextAreaElement>) {
+  return <textarea className={cn(fieldBase, "px-3 py-2 leading-relaxed", className)} {...rest} />;
+}
+
+export function Select({ className, children, ...rest }: SelectHTMLAttributes<HTMLSelectElement>) {
+  return (
+    <select className={cn(fieldBase, "h-9 cursor-pointer px-3", className)} {...rest}>
+      {children}
+    </select>
+  );
+}
+
+// Field 包一层标签 + 控件，统一表单纵向节奏。
+export function Field({ label, hint, children }: { label: string; hint?: string; children: ReactNode }) {
+  return (
+    <label className="flex flex-col gap-1.5">
+      <span className="text-[11px] font-medium text-slate-400">{label}</span>
+      {children}
+      {hint && <span className="text-[10px] text-slate-600">{hint}</span>}
+    </label>
+  );
+}